In vehicles with one or more automated clutches, regardless of whether the transmission is likewise automated, the clutch behavior is often modeled by software and is adapted at frequent intervals during driving operation. This permits the clutch to be actuated in such a way that the expectations of comfort and convenience from an automated clutch are met.
Clutch characteristic curves are often used for controlling automated clutches. Such clutch characteristic curves are representations of the torque transmissible by the clutch or clutches over the position of the actuator that disengages and/or engages the clutch. By means of such depictions, the torque transmissible by the clutch can be deduced from the position of the clutch actuator, or the position of the actuator can be deduced from the torque transmissible by the clutch.
Some of the clutch models also take dependencies on the clutch temperature into account, since that can lead to deformation of the clutch. A change in the clutch temperature can also lead to a change in the friction coefficient of the clutch lining.
Also considered are the engine speed, since high speeds of rotation can lead to centrifugal force effects, and also the slip speed, whose dependence is conditioned by the fluid in wet clutches.
However, clutches frequently exhibit hysteresis. Hence the torque transmissible by the clutch varies in magnitude, depending on whether the clutch is being disengaged or engaged at the time.
If allowance is not made for such hysteresis, this increases the scattering in the adaptive parameters of the clutch model. That causes the mean error in the clutch torque setting to rise, which can result in a reduction of driving comfort.